The invention described herein may be manufactured, used, and licensed by or for the United States Government for governmental purposes without the payment to us of any royalty thereon.
1. Field of the Invention
This invention relates to methods for extracting useful work from vortex rings and more specifically useful work such as pumps, filters and heat exchangers.
2. Discussion of Related Art
The vast majority of literature, patents, and dual-use products relate to monopole vortices, i.e., A spinning column of gas (tornado) or liquid (whirlpool) traversing normal to the vertical axis (see FIG. 1). Studies relate to weather prediction, flight safety through aircraft wingtip vortices, mixing in engines and appliances, etc. More recently, attention has been devoted to the ring-vortex, which is a gas or liquid torus spinning about the torus core and moving in a direction normal to the torus circumference (see FIG. 2). Typical interests are in transporting chemicals, momentum transfer to a target, contributions to turbulent flow, propeller noise and drag, fluid crash back against ship propellers, micro-bursts on the ground arising from propeller down wash or wind gusts, underwater sewage pipe backwash into the diffuser, etc.
No successful implementation of ring-vortex technology is found in military products. Commercial applications are only found for toy guns and theater cannons. One reason is a lack of engineering equations needed to design hardware for launching vortices with specified axial and spin velocities, forecasting the vortex resistance to dispersion in cross winds, forecasting resistance to shattering in wind gusts, estimating the in-flight leakage of chemicals being transported to a target, and estimating the loss of axial and angular momentum in flight. These gaps in technology arise from an incomplete understanding of the mechanisms of ring-vortex formation. As a result, the parameters critical to control to assure optimum vortex performance in flight and during target impact are unknown. Ring-vortex research has consequently centered on empirical trial and error, and no successful fielding of a device using a ring-vortex to perform useful work was found.
U.S. Pat. No. 5,823,434 shows a ring-vortex generator designed to launch an array of ring vortices spaced to avoid destructive interaction. Identical capabilities are defined in our invention but the primary difference is a fluidic flip-flop pressure pulse generator is used to launch vortices rather than a vibrating membrane. The advantage is operational flexibility; i.e., adjusting the flip-flop frequency alters the axial spacing between ring vortices, and regulating manifold pressure controls the angular and axial momentum of each ring-vortex.
A report entitled xe2x80x9cControl of vortex breakdown in a rotating flow: Numerical Simulationxe2x80x9d authored by Nadine Aubry et. al. (DFD98 Meeting of The American Physical Society, Nov. 23, 1998) describes a rod placed along the axis of a vortex. Our invention places a rod along a ring-vortex axis of propagation, but the mechanics and objectives are different. In the cited report, the vortex is a mono-pole (whirlpool), the rod is spinning, the rod is placed along the low-pressure whirlpool axis, and the objective is to prevent the formation of ring vortices that tend to destroy the whirlpool. Our invention addresses a dipole (torus) vortex, the rod is placed normal to, and mid-way between the two axis of revolution, and the objective is to create a surface area in the region of highest velocity for the purpose of extracting useful work from the vortex.
A report entitled xe2x80x9cNumerical and experimental study of the interaction between a vortex dipole and a circular cylinderxe2x80x9d authored by R. K. Verzicco et. al. (Exp. Fluids 18, 153-163) discusses a ring-vortex interaction with a circular rod, as does our invention. In this report, the ring-vortex motion is perpendicular to the rod, and the goal was to examine the change in the free surface since this is relevant to sound generation. In our invention, the ring-vortex is concentric with the rod, moves along the axis of the rod, and performs work on the rod.
Accordingly, it is an object of the present invention to describe methods for extracting useful work from a ring-vortex
It is another object of the invention to describe useful ring-vortex work items such as pumps, filters and heat exchangers.
The foregoing and other objects are achieved by the several methods presented for extracting useful work from a ring-vortex moving at high angular and axial velocities. The key components are a ring-vortex generator or launcher, a platen that penetrates the ring-vortex centroid along the axis of revolution, and a collector. Typical applications that utilize different parameters of a ring-vortex include a pump, filter, and heat exchanger.
The launcher will launch a gas or liquid ring-vortex around the circumference of a platen and toward a collector. For compressible flow the nozzle of the launcher may be designed to form vortices from subsonic or supersonic jet streams. In the latter instance, designing the nozzle to achieve atmospheric pressure at the exit maximizes the velocity and spin at which the ring-vortex is launched from the jet stream. To improve efficiency, a chain of vortices may be launched and harvested.
The collector will retrieve materials entrained by the ring-vortex for the purpose of disposal or salvage. The location may be downstream or at the end of the platen, at the launch site when a reflector is placed opposite the launcher, or absent if other means of collection are used
One purpose of the platen is to guide the ring-vortex from the launcher to the collector. The reason is that cross-flow against a platen with a traversing vortex generates magnus forces that promote dispersion. The platen establishes a resisting torque that maintains the course of ring-vortex propagation. Another purpose of the platen is to provide a large surface area in the region of highest ring-vortex velocity. The platen surface may be irregular as shown in FIG. 4 if the shape does not destroy the vortex integrity. An illustrative example in FIG. 4 is longitudinal fins
The vortex-ring will perform work on the platen surface using the inherent properties of the torus core and the trailing wake. The work performed by the ring-vortex depends upon the configuration of the platen.
When used as a pump, the platen is a flexible tube containing a fluid or gas, and the critical ring-vortex parameter of interest is the pressure distribution on the platen. The launcher forms a ring-vortex around the tube circumference, and a high circumferential pressure forms at the bow and a low pressure forms at the wake of the vortex-ring. The flexible platen compresses and expands accordingly, and as the ring-vortex moves, the pinching action also moves and pumps the material inside the tube.
As a filter, the platen is configured electrically, mechanically, thermally, magnetically, chemically, or otherwise to form surface deposits or to extract materials from the surrounding environment. The ring-vortex mechanically abrades the platen surface, fractures the adhesion bonds of surface residues, lifts the residues from the surface, entrains the residues in the torus core, and transports the residues to the collector for recovery or disposal. Typical surface residues are gas bubbles, condensates, dirt, salts, rust, metal chips, etc. The critical parameters are the angular momentum about the torus core, the height of the torus core center above the platen, and the axial momentum.
When used as a heat exchanger, the platen is a heated bar and the ring-vortex transfers heat by means of forced convection. The critical parameters are spin and axial velocities and the direction of flow. Traditional heat exchangers of this type utilize coolant flows that are normal to or in-line with the platen, and their performances are degraded by boundary layers and flow separations that reduce the coolant velocity and the area of contact. The ring-vortex is not subject to these limitations for the reasons described below.
The ring-vortex is unique in that it subjects the platen to both types of flow simultaneously; i.e., the spinning torus directs flow into and away from the surface in a nearly perpendicular fashion and flow in the wake is largely parallel to the platen. Additionally, the ring-vortex is unique in that the velocity within the torus is the vector sum of the angular and axial velocities and high Reynolds numbers are achieved without boundary layers that degrade the film coefficient of heat transfer and without the loss of laminar flow needed to entrain particulates in the torus core. Finally the ring-vortex encircles the platen and traverses the length, thereby assuring contact with the entire surface area.
The ring-vortex may be used to transfer heat in a stand-alone fashion or in conjunction with the traditional cross-flow and in-line designs. In the latter mode the ring-vortex will reduce maintenance and operating costs by removing surface contaminants that degrade the surface conductance, film coefficient, and emissivity of the platen and thereby degrade efficiency.